U.S. patent application number 13/298785 was filed with the patent office on 2012-05-24 for interface between a security module and a host device.
This patent application is currently assigned to NAGRAVISION S.A.. Invention is credited to Ernest Odoom, Karl OSEN.
Application Number | 20120127672 13/298785 |
Document ID | / |
Family ID | 46064222 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120127672 |
Kind Code |
A1 |
OSEN; Karl ; et al. |
May 24, 2012 |
INTERFACE BETWEEN A SECURITY MODULE AND A HOST DEVICE
Abstract
The present invention may be deployed in a system comprising a
security module housed on a chip card and a host device comprising
a chip card reader. The host device is comprised in a housing with
a slot for the chip card. The housing is shielded to reduce the
amount of electromagnetic radiation generated by the security
module and/or the host device from penetrating to the exterior of
the housing. Similarly, the shielding is adapted to reduce the
effects of electromagnetic radiation generated outside of the host
device on the components within the housing. The slot is also
shielded by a flap made of an electrically conductive epoxy
material or an electrically conductive resin.
Inventors: |
OSEN; Karl;
(Cheseaux-Sur-Lausanne, CH) ; Odoom; Ernest;
(Geneva, CH) |
Assignee: |
NAGRAVISION S.A.
CHESEAUX-SUR-LAUSANNE
CH
|
Family ID: |
46064222 |
Appl. No.: |
13/298785 |
Filed: |
November 17, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61414907 |
Nov 18, 2010 |
|
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|
Current U.S.
Class: |
361/728 |
Current CPC
Class: |
G06F 1/182 20130101;
H05K 9/0018 20130101 |
Class at
Publication: |
361/728 |
International
Class: |
H05K 7/00 20060101
H05K007/00 |
Claims
1. An interface module for providing an electrical interface
between a security module and a host device, said interface module
comprising: a housing: and an electronic component disposed within
the housing, the electronic component having at least one contact
configured to make electrical contact with a corresponding contact
on the security module; wherein the housing has a slot formed
therein, the slot being sized and shaped to allow the security
module to be inserted therethrough, the housing further comprising
a movable slot shield for substantially attenuating through
propagation of electromagnetic interference generated inside the
housing or generated outside the housing, said movable slot shield
being made from one of electrically conductive epoxy or
electrically conductive resin, the movable slot shield being
configured to allow passage of the security module through the slot
such that the contact of the electronic component contacts the
corresponding contact on the security module.
2. The interface module according to claim 1, wherein a slit is
formed in the movable slot shield, the slit being formed to allow
insertion of the security module through the slit.
3. The interface module according to claim 1, wherein at least part
of the movable slot shield is fixed to the housing by gluing,
welding or soldering, said movable slot shield having elastic
properties sufficient to allow at least part of the movable slot
shield to move in order for said passage of the security module
through the slot, said elastic properties being further sufficient
to provide movement of the part of the movable slot shield to a
position allowing for said attenuation.
4. The interface module according to claim 1, wherein the movable
slot shield comprises a piece of material sufficiently large to
cover the slot, said slit being formed by making a cut through the
material, the cut being of sufficient dimension to allow the
passage of the security module.
5. The interface module according to claim 1, wherein the movable
slot shield comprises a first piece of material and a second piece
of material, the first piece of material being attached to the
housing on a first side of the slot thereby leaving at least one
edge of the material free, the second piece of material being
attached to the housing on a second side of the slot thus leaving
at least one edge of material free, the pieces of material being
positioned such that the free edge of the first sheet touches the
free edge of the second sheet, said slit being formed along a line
where the first and second sheets meet.
6. The interface module according to claim 1, wherein the movable
slot shield comprises a first piece of material and a second piece
of material, the first piece of material being attached to the
housing on a first side of the slot thereby leaving at least one
edge of the material free, the second piece of material being
attached to the housing on a second side of the slot thus leaving
at least one edge of material free, the pieces of material being
positioned such that the free edge of the first sheet overlaps the
free edge of the second sheet, said slit being formed along said
overlap, said overlap being of an amount which is sufficient to
allow insertion of the security module through the slit.
7. The interface module according to claim 1, wherein the housing
is made from a conductive material, said housing being electrically
grounded.
8. The interface module according to claim 1, wherein at least one
pathway extending from a point where the electrical contact is made
is covered by alternate layers of one of non-conducting and
conducting adhesives, non-conducting and conducting tapes,
non-conducting and conducting resins or non-conducting and
conducting epoxies.
9. The interface module according to claim 1, wherein it is
included into the host device.
10. An interface module for providing an electrical interface
between a security module and a host device, said interface module
comprising: a housing; and an electronic component disposed within
the housing, the electronic component having at least one contact
configured to make electrical contact with a corresponding contact
on the security module; wherein at least one pathway extending from
a point where the electrical contact is made is covered by
alternate layers of one of non-conducting and conducting adhesives,
non-conducting and conducting tapes, non-conducting and conducting
resins or non-conducting and conducting epoxies.
11. The interface module according to claim 10, wherein it is
included into the host device.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. Section 119
to U.S. Provisional Application No. 61/414,907, filed Nov. 18,
2010, the entire contents of which are hereby incorporated by
reference herein.
INTRODUCTION
[0002] The present invention relates to the domain of radio
frequency electromagnetic interference and more specifically to
methods and devices for the reduction of such interference in
electronic circuits.
STATE OF THE ART
[0003] With the increasing use of higher and higher signal
frequencies in the operation of electronic circuits, the problems
related to electromagnetic interference or EMI are becoming more
acute. In the domain of conditional access, the use of a security
module is commonplace. A security module is usually used in
cooperation with a host device which comprises at least a card
reader to interface with the security module. The host device may
further comprise a cryptographic module and other related
conditional access hardware and software. The security module holds
personalised information such as cryptographic keys and the like,
which need to be kept secret. The security module is generally a
portable device which is detachable from the host device.
[0004] A common example of a security module is an electronic chip
housed on a card, generally in the form of a credit card, a SIM
card or a micro-SIM card or other similar support. The card is
usually presented to the host module, or more particularly to the
card reader within the host module, via a slot in the host module.
Contact is made between the chip and the card reader by a set of
contacts which come to rest on a set of corresponding contact pads
on a surface of the card, which connect to the chip.
[0005] With the tendency for operating frequencies of the
aforementioned security modules to be higher, i.e. in ranges in
excess of several hundreds of megahertz, any connections to the
security module which carry signals with frequency components in
such ranges, namely connections to clock and data pins for example,
will tend to emit electromagnetic radiation. Such electromagnetic
radiation may be intercepted by a third party and used to breach
the security of the security module, For example by monitoring the
electromagnetic radiation during the time that the security module
transmits a secret key, it may be possible for a third party to
reconstruct the secret key for malicious purposes. Similarly, a
security module may be susceptible to interference by sufficiently
strong electromagnetic fields generated externally to the security
module for the purpose of influencing the operation of the security
module and/or card reader during operation. Such interference,
generated either externally or internally by the security module or
any of the other circuitry within the host during operation, is
known as electromagnetic interference or EMI.
[0006] The EMI phenomenon is well known in the electronics
industry. Indeed, there are industry-standard limits placed on
electronic circuits relative to the amount of electromagnetic
radiation such circuits are allowed to generate. These limits are
designed to minimise the possibility of circuits susceptible to
generating large quantities of EMI from affecting neighbouring
circuits and to avoid the risk of physical harm to humans in the
vicinity of such circuits.
[0007] It is usual, in the domain of electronic circuits which are
designed to operate at radio frequencies (RF), to enclose such
circuits within a box whose walls are entirely covered by a
material which has the properties of providing shielding against
electromagnetic radiation. This generally provides sufficient
protection against radiation produced by the circuit from escaping
towards the outside of the enclosed box and against radiation
generated outside of the box from penetrating into the box and
interfering with the operation of the circuit.
[0008] However, in the case of a host device designed to receive a
security module via a slot or port, it is difficult to prevent EMI
from escaping since the port presents a discontinuity in the
enclosure and therefore a discontinuity in the shielding thereby
exposing an area where EMI may escape. U.S. Pat. No. 7,321,919 B1
describes a port cover for limiting transfer of electromagnetic
radiation from the port of a host device when the security module
is functioning within the port. A port cover is mounted over the
slot for the chip card after the chip card is entered. The port
cover is lined with a conductive material, which contributes to the
EMI shielding properties of the port cover and permits for an
electrical circuit to be completed when the port cover is in
position, thus allowing for the detection of whether or not the
port cover is properly closed.
[0009] There also exist devices for providing a shield around
electronic components susceptible to emitting EMI such as the
device described in U.S. Pat. No. 5,436,803 which teaches of a
flexible envelope surrounding an electronic circuit card within the
host device, the electronic circuit card comprising the offending
component. The flexible envelope comprises an insulating sheet such
as polyethylene and a sheet of conductive fibres such as metalised
nylon giving a resistivity in the order of a tenth of an ohm.
Another example is described in International Patent Application
Publication number WO 2005/106953 A1, which discloses a screening
layer, comprising a layer of soft magnetic material of high
relative permeability such as iron, nickel or cobalt or any of
their alloys, placed on the surface of the component susceptible to
emit the offending EMI. The document further goes on to describe
the use of a further layer of additional hard material, such as
diamond-like carbon, on the surface of the offending component to
prevent access to the component through mechanical or chemical
means.
BRIEF SUMMARY OF THE INVENTION
[0010] In view of the prior art, it is an aim of the present
invention to provide a means for reducing the amount of
electromagnetic interference detectable from the outside of a host
device while the host device is communicating with a security
module, especially when the host device comprises a slot or port
through which the security module is inserted.
[0011] It is a further aim of the present invention to provide a
means for reducing the amount of electromagnetic interference
escaping from a security module towards electronic components
comprised within a host device while the security module is
communicating with the host device.
[0012] It is a further aim of the present invention to provide for
such reduction in electromagnetic interference while retaining ease
of physical access to the host device by the security module,
thereby allowing ease of exchanging one security module for
another. This requirement therefore precludes the possibility of
using a port cover or a flexible envelope as described in the prior
art as well as the use of screening layers around the security
module. Additionally, an aim of the present invention is to reduce
the manufacturing costs associated with the production of host
devices intended to receive security modules which function at
operating frequencies high enough to generate the undesired EMI and
therefore the use of expensive screening layers such as those
described in the prior art is not a desired option.
[0013] The aims of the present invention are therefore achieved by
providing an interface module for providing an electrical interface
between a security module and a host device, said interface module
comprising: [0014] a housing; and [0015] an electronic component
disposed within the housing, the electronic component having at
least one contact configured to make electrical contact with a
corresponding contact on the security module; [0016] wherein the
housing has a slot formed therein, the slot being sized and shaped
to allow the security module to be inserted therethrough, the
housing further comprising a movable slot shield for substantially
attenuating through propagation of electromagnetic interference
generated inside the housing or generated outside the housing, said
movable slot shield being made from one of electrically conductive
epoxy or electrically conductive resin, the movable slot shield
being configured to allow passage of the security module through
the slot such that the contact of the electronic component contacts
the corresponding contact on the security module.
[0017] There is also provided an interface module for providing an
electrical interface between a security module and a host device,
said interface module comprising: [0018] a housing; and [0019] an
electronic component disposed within the housing, the electronic
component having at least one contact configured to make electrical
contact with a corresponding contact on the security module; [0020]
wherein at least one pathway extending from a point where the
electrical contact is made is covered by alternate layers of one of
non-conducting and conducting adhesives, non-conducting and
conducting tapes, non-conducting and conducting resins or
non-conducting and conducting epoxies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will be better understood thanks to
the detailed description which follows and the accompanying
drawings, which are given as non-limiting examples of embodiments
of the invention, where:
[0022] FIG. 1 shows a chip card with a security module inserted
through a flap into a housing according to an embodiment of the
present invention.
[0023] FIG. 2 shows a housing for an interface module, the housing
having a slot which is covered by a material having elastic
properties, with a slit being cut in the material, the cut being
suitable for a chip card to pass through, while the elasticity of
the material is sufficient to form a seal around the card.
[0024] FIG. 3 shows a housing for an interface module similar to
that in FIG. 2 but where the covering for the slot is made by
attaching two pieces of flexible material to the housing in such a
way that the slit is formed between the two pieces of material.
[0025] FIG. 4 shows a variation of the embodiment of FIG. 3.
DETAILED DESCRIPTION
[0026] In a system comprising a host device and a detachable
security module (CH), wherein the a card reader within the host
device is adapted to form an interface with the detachable security
module (CH), at least some of the signals in the interface will
carry high frequency signals susceptible to producing or being
affected by electromagnetic interference. Depending on the design
of the host device and any components therein, there may be further
areas within the host device which are susceptible to EMI.
According to an embodiment of the present invention, techniques are
employed to provide means to minimise the amount of EMI from
penetrating from the interior of the host device to the exterior or
from the exterior to the interior. For example, any connections
carrying signals having a frequency component are kept as short as
possible as it is known that the length over which a high frequency
signal is present is a significant variable contributing to the
amount of EMI emitted. Additionally, these lines are preferably
made from shielded cabling,
[0027] According to an embodiment of the present invention, a
shield is built to substantially reduce any EMI generated inside
the host device from penetrating to the outside of the host. in
this embodiment, the shield is in the form of a flap (FLP) covering
the port or slot (SLT) of the host device through which the chip
card (CC) which comprises the security module (SM) is inserted. The
flap (FLP) is made of an electrically conductive epoxy material or
an electrically conductive resin and is suitably dimensioned and
positioned so as to adequately enclose the chip card (CC) as it is
inserted into the slot (SLT). In this manner, since the epoxy or
resin exhibits elastic properties, a seal is formed around the chip
card (CC) when it is inserted into the slot (SLT). Since the epoxy
or resin is electrically conductive, the flap (FLP) provides EMI
shielding such that any EMI generated within the host device does
not propagate outside of the host device or is at least
substantially attenuated so as not to be considered a problem.
According to variants of this embodiment of the invention, the flap
(FLP) may be formed by one sheet of the epoxy or resin, attached to
either the top or bottom of the slot (SLT) or the flap (FLP) can be
made from a larger sheet of the epoxy or resin with a slit cut near
the middle of the sheet to receive the chip card (CC) or the flap
(FLP) may be realised by two sheets of epoxy or resin material, the
two sheets being suitably fixed to the slot (SLT) such that the
edges of the two sheets come together thus forming the flap (FLP)
near the middle of the slot (SLT). Since the flap, or flaps, is
(are) made of epoxy or resin, thanks to their elasticity they can
be simply fixed to the housing by simple fastening, clipping,
gluing, soldering or welding for example, without the need for any
additional fixtures such as hinges or the like. The elasticity of
the flap(s) suffices for the desired effect of allowing the chip
card to be inserted while providing a seal sufficient to
sufficiently attenuate through-propagation of EMI, either from
inside the housing to the outside or vice-versa.
[0028] FIG. 2 shows a cross-sectional view of a housing for an
interface module in which an embodiment of the present invention
may be deployed. The drawing illustrates the end of the housing
which is adapted to receive the chip card. The housing (HSE) has a
slot (SLT) which is covered by a material having elastic properties
(FLP), The flap is made from a single sheet of material, which may
be electrically conductive epoxy or electrically conductive resin
for example. The material is attached to the housing in a way which
results in the slot being entirely covered by the material. At the
level of the slot in the housing, a cut has been made in the
material, forming a slit (ST). The cut is sufficient in shape and
size for a chip card to be inserted through the slot and into the
housing. Thanks to the elastic properties of the material, the
material around the cut will be urged against the card thereby
forming a seal around the card.
[0029] FIG. 3 shows a housing for an interface module similar to
that in FIG. 2 but where the flap comprises two sheets of the
material. Each piece of the flexible material is attached to one
and another side of the slot (SLT) in the housing (HSE) such that
at the place where both sheets meet, they at least touch each
other, thereby creating, at the part where they touch, the slit
(ST) through which the chip card can pass. Preferably the sheets
will overlap sufficiently for the card to be able to pass through
and for the elasticity of the flaps to allow for a suitable seal to
be formed around the card once inserted. In FIG. 4, the flap, or
movable slot shield, is made from two pieces of the material having
elastic properties, wherein each of the pieces is attached to a
part of the slot in a way that they reduce the size of the slot to
a slit just wide enough for the chip card to be inserted. The
material is tapered in such a way that it remains flexible enough,
at the area where the two pieces meet, such that the card can be
introduced through the slit, the elasticity of the material
ensuring a sufficient seal around the card.
[0030] According to a further embodiment of the present invention,
a reduction in the amount of EMI escaping from the inside of the
host device towards the outside is achieved by making a housing
(HSE) for the host device, or at least for the components of the
host device which are susceptible to producing EMI, from a
conductive plastic material and by electrically grounding the
housing. These materials provide shielding for EMI due to their
conductive properties and do not require the additional steps of
adding conductive layers or conductive paint and therefore
contribute towards minimising the manufacturing cost of a housing
(HSE) providing EMI shielding.
[0031] It is worth noting that the shielding effect afforded by any
of the embodiments of the present invention in which a shield is
employed serves not only to reduce the amount of EMI penetrating
from the inside of the host device to the outside, but it further
serves to reduce the amount of EMI penetrating into the host from
outside and thereby reduces the possibility of the components
within the housing (HSG) being affected by interference from
outside.
[0032] In another embodiment of the present invention, provision is
made to shield the EMI generated by pathways carrying high
frequency signals from contaminating other electronic circuits
within the host device and from escaping outside of the host
device. Preferably, if measures have been taken to minimise the
number of pathways concerned and to reduce to reduce the lengths of
such pathways to a minimum, then the aforementioned provision is
readily realisable. In this embodiment, as well as making use of
the shielding flap (FLP) as described above to prevent EMI from
escaping from the host, use is made of a shielding box which
isolates those pathways carrying high frequency signals. For
example, in an interface between a card reader and a security
module (CH) housed on a card or chip card (CC), at least two
pathways input/output (IO) and clock (OK) require to be isolated.
The offending pathways are geographically isolated and physically
located in a region near the slot (SLT) of the host, where they
will come into contact with the security module (CH). The flap
(FLP) is used to isolate the EMI generated by the pathways from the
outside of the host. This isolation is completed by the fact that
the host is housed in either a metal box or a box made from
conductive plastic as described above. This box is referred to as a
housing (HSE). Furthermore, in order to isolate the EMI from the
rest of the host's electronic components, a wall is made within the
housing (HSE) either from metal or from conductive plastic and
electrically grounding it to electromagnetically isolate the
offending pathways from the rest of the circuitry in the host
device. According to another embodiment, instead of simply forming
a wall, the grounded metal or conductive plastic may be shaped to
enclose the offending pathways and connect to the flap (FLP), thus
creating an EMI-impermeable box within the host device. Joints
between the metal or conductive plastic are preferably sealed with
electrically conductive epoxy resin as are gaps between the
conductive plastic or metal and the flap thereby assuring a maximum
isolation.
[0033] Conversely, or in combination, as in another embodiment of
the present invention, instead of enclosing the offending pathways
in an EMI-shielded enclosure, the rest of the circuits in the host
device, which may be susceptible to EMI coming from the
high-frequency pathways mentioned above, may be insulated from
externally-generated EMI by covering them with EMI-shielding
conductive epoxy or by wrapping them with EMI-shielding conductive
tape. As with all of the techniques involving electrically
conductive adhesives. tapes, resins or epoxies, such treatment may
be part of a multi-layer treatment where alternating layers of
non-conducting and conducting materials, such as adhesives, tapes,
resins or epoxies, are applied. Indeed, such materials are known to
exist in non-conducting form and in conducting form. A conductive
path of a circuit to be protected in this way will thus first be
covered with a layer of such a non-conducting material followed by
a layer of such a conducting material.
[0034] If any of the mentioned high-speed pathways require to cover
more than the minimum possible distance, it is preferable to
convert such signals to a differential signal over two pathways
located in close proximity--preferably adjacent to each other at
minimum pitch or, if such pathways exist as wires, then as a
twisted pair. The signals should preferably be of a current mode,
of minimum common-mode voltage level and have a minimal voltage
swing between logic states. A low-voltage differential protocol
such as the communication protocol known as LVDS is well-suited for
such pathways. According to another embodiment of the present
invention, LVDS drivers are used to convert the clock signal from a
single-ended wire to a two-ended differential current mode bus
terminated with a hundred ohm resistor and conforming to the LVDS
communication protocol. One end of the two-ended bus is used to
drive the clock pad of the security module. Similar drivers are
used to convert the input/output signal to be compatible with the
LVDS protocol.
* * * * *